Inline below. -- Bert
On Mon, Jul 2, 2012 at 8:04 AM, David Winsemius <dwinsem...@comcast.net>wrote: > > On Jul 2, 2012, at 10:51 AM, David Winsemius wrote: > > >> On Jul 2, 2012, at 9:29 AM, YTP wrote: >> >> I would like to specify a model with all polynomial interaction terms >>> between >>> two variables, say, up to degree 6. For example, terms like a^6 + (a^5 * >>> b^1) + (a^4 * b^2) + ... and so on. The documentation states >>> >>> The ^ operator indicates crossing to the specified degree. >>> >>> so I would expect a model specified as y ~ (a+b)^6 to produce these >>> terms. >>> However doing this only returns four slope coefficients, for Intercept, >>> a, >>> b, and a:b. Does anyone know how to produce the desired result? Thanks >>> in >>> advance. >>> >> >> You might try: >> >> poly(a,6)*poly(b,6) >> >> (untested ... and it looks somewhat dangerous to me.) >> > > Well, now it's tested and succeeds at least numerically. Also tested > > ( poly(a,6) +poly(b,6) )^2 with identical results. > > Whether this is wise practice remains in doubt: > No it doesn't. It isn't. -- Bert > > dfrm <- data.frame(out=rnorm(100), a=rnorm(100), b=rnorm(100) ) > anova(lm( out ~ (poly(a,6) +poly(b,6) )^2, data=dfrm) ) > #----------------------- > Analysis of Variance Table > > Response: out > Df Sum Sq Mean Sq F value Pr(>F) > poly(a, 6) 6 12.409 2.06810 3.0754 0.01202 * > poly(b, 6) 6 5.321 0.88675 1.3187 0.26596 > poly(a, 6):poly(b, 6) 36 41.091 1.14142 1.6974 0.04069 * > Residuals 51 34.295 0.67246 > --- > Signif. codes: 0 *** 0.001 ** 0.01 * 0.05 . 0.1 1 > > -- > > David Winsemius, MD > West Hartford, CT > > ______________________________**________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help> > PLEASE do read the posting guide http://www.R-project.org/** > posting-guide.html <http://www.R-project.org/posting-guide.html> > and provide commented, minimal, self-contained, reproducible code. > -- Bert Gunter Genentech Nonclinical Biostatistics Internal Contact Info: Phone: 467-7374 Website: http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm [[alternative HTML version deleted]]
______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
